Psychiatric Disorders in Dementia

Alzheimer’s disease (AD) is the most common form of dementia, a neurodegenerative disorder which is characterized not only by cognitive deterioration but also by a diversity of behavioral and psychological signs and symptoms of dementia (BPSD). BPSD in AD or other dementia subtypes such as frontotemporal dementia (FTD) or dementia with Lewy bodies (DLB) consist of delusions, hallucinations, activity disturbances, aggression/agitation, diurnal rhythm disturbances, mood disorders, apathy, and anxieties/phobias. Neuroimaging modalities such as positron emission tomography (PET) and single-photon emission computed tomography (SPECT) are very essential and useful imaging tools to differentially diagnose between AD and non-AD or healthy control subjects or between different dementia subtypes, such as AD and DLB or FTD. Besides their diagnostic utility, PET and SPECT are useful tools to investigate the cerebral pathophysiology of BPSD in dementia.Below, PET and SPECT neuroimaging research in dementia spanning the last three decades has been systematically reviewed. The most commonly used PET and SPECT radioligands, as well as new developments in the field, all targeting different and unique aspects of neurodegeneration, are described. Furthermore, PET and SPECT research in BPSD with a main focus on depression, apathy, and psychosis in AD, DLB, and FTD are discussed in detail. On the whole, both PET and SPECT have demonstrated that depending on the behavioral phenomenon and dementia subtype, BPSD are the fundamental expression of very regional cerebral pathological events rather than a diffuse brain illness